Abstract

Oxygen plasma treatment has been extensively used to functionalize the surface of graphenelike materials. However, functionalization is usually accompanied by degradation of the structure, which may affect mechanical and electrical performance. Atmospheric plasma treatment (APT) of HOPG was performed to compare the effect of surface modification using carbon monoxide (CO) as the active gas, in comparison to O2. Both Raman and STM demonstrated nanoscale degradation of the structure when using the O2treatment. CO treated specimens exhibited no observable damage to the material with high levels of oxygen incorporation. Instead, a well ordered monolayer of oxygen-containing film was observed on the surface of the specimens which could accommodate high levels of surface oxygen. Changes in surfacecharacteristics were analyzed using x-ray photoelectron spectroscopy(XPS) as a function of duration. The results indicated that the use of O2plasma resulted in only a limited oxygen uptake (O/C = 0.11), while CO APT resulted in tailorable surface O/C ratios as high as 0.65, a result not observed even when using low-pressure radio frequency plasmas.XPS analysis and Auger spectroscopy confirmed that a tailorable level of carbonyl functional groups could be evenly distributed throughout the surface. Contact angle measurements verified the formation of a highly stable hydrophilic surface. The CO treatment was also successfully applied to other nanocarbon materials such as graphene nanoplatelets with similar results.